Sealless strap connection



Feb. 14, 1967 J. R. BEACH SEAL-LESS STRAP CONNECTION Filed Oct. 22, 1965 United States Patent 3,303,541 SEALLESS STRAP CONNECTION John R. Beach, Elmhilrst, llll., assignor to Signode Corporation, a corporation of Delaware Filed Oct. 22, 1965, Ser. No. 501,725 3 Claims. (Cl. 24-20) This invention relates to metal strapping and, more particularly is concerned with sealless connections between overlapped lengths of metal strap. This application discloses an improvement on the arrangement disclosed in pending application, Serial No. 468,320, filed June 30, 1965.

It has long been conventional practice to provide sealless connections between strap ends in the form of a tandem array of longitudinally spaced shear lock joints. The most popular form of shear lock joint utilizes a central tongue provided with lateral wing extensions partly along its opposite edges. The width of the wing extensions reduce the effective cross section of the strap and hence reduce its load handling strength.

Many variations from this double wing tongue pattern have been suggested over the years and this is evidenced by numerous prior art patents on this subject including Anderson No. 1,606,331, Leslie No. 2,268,339 and No. 2,276,988, Mosey No. 3,137,047 and Timmerbeil No. 3,177,538. All of these patents are subject to the defect of unduly reducing the effective cross section of the strap.

The present invention provides a sealless connection wherein a higher strength joint is realized and lateral pull out action is avoided or minimized.

A sealless connection in accordance with the present invention employs a tandem array of longitudinally spaced joints connecting a pair of strap ends against pull out wherein in each joint, each strap section has a single staggered slit defining and flanked by complementary integral strap web portions that are offset in opposite normal directions. The complementary strap web portions provide lengthwise'aligned shoulders matched to corresponding shoulders on the other strap section and minimizing strap width reduction.

The staggered slits are essentially lengthwise oriented and at least some have substantially right angle intermediate jogs presenting substantially transverse shoulders. Each slit strap section has one of its transverse shoulders enterable lengthwise into an opposing slit end region of the mating strap section so that each joint has opposed slit end regions each receiving a separate transverse shoulder in interlocking relation. The right angled transverse shoulders avoid lateral wedging effects and thereby avoid lateral pull out effects.

The staggered slits are also aligned and centered to balance out the force transmitting areas of the strap web portions that flank each slit. Unbalanced areas promote a twist effect about a fulcrum point defined at each interlocking shoulder region and lead to strap breakage which usually begins at one of the endmost joints. Centered and aligned slits avoid this twist effect.

In the entire array, the pattern of single slits is arranged in a symmetrical or balanced fashion.

Other features and advantages of the invention Will be apparent from the following description and claims, and are illustrated in the accompanying drawings which show an illustrative embodiment of the present invention.

In the accompanying drawings forming a part of the specification, and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a fragmentary plan view of overlapping lengths of strap nested in full registry in preparation for offset movement into interlocking relation;

FIG. 2 is an enlarged fragmentary plan View of the strap ends of FIG. 1 before nesting of the same;

' 3,303,541 Patented Feb. 14, 1967 "ice FIG. 3 is a side elevational View of the strap ends pictured in FIG. 2;

FIG. 4 is a fragmentary perspective view of portions of the strap lengths pictured in FIG. 1 and showing the same interlocked; and

FIG. 5 is a fragmentary plan view of one strap end in accordance with an alternative embodiment of the invention.

Referring now to the drawings, upper and lower overlapped lengths of metal strap 20 and 30, respectively, are shown for tension transmitting inter-engagement by means of a sealless strap connection defined therebetween. Such sealless strap connections conventionally include a tandem array of longitudinally spaced shear lock joints, six of which are shown in FIG. 1. The particular sections of strap which overlap and interlock to make up each joint are configured to nest substantially fully to enable the overlapping lengths 20 and 30 to engage in substantially full surfaced contact. In a six joint connection array, each strap length has six such nestable sections.

Each of the nestable strap sections of the upper strap 26, as best seen in FIGS. 2 and 3, is characterized by a lengthwise directed staggered slit 22 defining and flanked by complementary strap web portions 23U and 24D that integrally merge endwise with full body regions of the strap and that are offset in opposite normal directions from the plane of the strap. The web portions 23U are offset upwardly and each presents a shoulder 23S and the web portions 24D are offset downwardly and each presents a shoulder 248. Thus, the shoulders 23S and 248 are lengthwise aligned but offset in a direction normal to the plane of the strap. Each staggered slit 22 has lengthwise directed end regions 25, 26 bridged by an intermediate lateral jog region 27.

Correspondingly, each of the nestable strap sections of the lower strap 30 is characterized by a substantially identical lengthwise directed slit 32 defining and flanked by complementary strap web portions 33U and 34D presenting shoulders 33S and 348, respectively, that are normal to the plane of the strap. Each staggered slit 32 has lengthwise directed end regions 35, 36 bridged by an intermediate lateral jog region 37.

The assembly and completion of the sealless connection is accomplished by first nesting the strap lengths 20 and 30 in their position of full registry as shown in FIG. 1. In this position and considering the completed joint shown at the extreme left in FIG. 4, each nestable strap section of such joint presents a locking shoulder 24S and 338 that nests in the jog region of the slit in the other section. Thus, shoulder 24S nests in the jog region 37 in preparation for endwise entry into slit end region 36 and shoulder 33S nests in the jog region 27 in preparation for entry into the slit end region 25. Thereafter the strap lengths 20 and 30 are shifted longitudinally to effect one way mutual interlocking relationship between the shoulders 33S and 24S and slit end regions 25 and 36, respectively. The final mechanical interlock relationship is illustrated in FIG. 4.

In the embodiment disclosed in FIGS. 1 to 4, the lateral jog regions of the staggered slits 22 and 32 are essentially transverse and correspondingly the interlocking shoulders are right angled. These interlocking shoulders create an essentially lengthwise directed reaction effect free of lateral wedging effects.

The staggered slits are centered and aligned and arrayed in a balanced pattern in that certain of the slits jog in one lateral direction and others jog in an opposite lateral direction. A staggered slit is here said to be centered when the midpoint of the lateral jog region is on the strap centerline. For this condition the flanking strap web portions are equal in effective cross section and the forces transmitted by the strap balance out about the fulcrum point established by the interlocking shoulder, thus avoiding strap twisting effect.

When strap joints are stressed to failure, the failure may be of the break type or the lateral pull out type. In the disclosed configuration, the connections produced when the stamping die is new and wear free are arranged to provide a break type failure. Upon wear of the tool, the slit configuration varies slightly particularly at the jog region and the connections then produced give the lateral pull out type of failure, and actually achieve greater failure strength. Continued wear of the tool, thereafter, leads to weaker joints.

It should be noted that each of the slits 22, 32 may be provided with a straight companion slit to provide a laterally facing abutment for preventing lateral pull out movement but with the centered right angled slit configuration, these companion slits are not required. It is contemplated to use such companion slits where the staggered slits are off the strap center-line.

An alternative slit configuration for use in a sealless strap connection is illustrated in FIG. wherein one strap end is shown having staggered right angle slits 22 at opposite ends and having intermediate staggered slits 42 having angled jog regions 47. V

In the present disclosure, the sealless joints are provided in heat treated strap that is inch by 0.025 inch. A total of siX joints are provided and the offset dimension for each staggered slit is about percent of the strap width. Each joint region is therefore about 90 percent as strong as the strap. Where each slit is of the same offset dimension, ultimate failure occurs at the end slit. The effective combined strength of the joint can be increased somewhat by utilizing end slits of slightly less offset dimension than that of the intermediate slits.

Thus, while preferred constructional features of the invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In a sealless strap connection between overlapped lengths of metal strap, a tandem array of longitudinally spaced shear lock joints, each joint being defined between nestable strap sections provided by matched integral portions of each length of metal strap, said nestable strap sections that define each joint being partly offset longitudinally to engage in one Way mutually interlocking relation, each said nestable strap section having a single longitudinally oriented staggered slit comprised of lengthwise slit end regions and a lateral jog region joining the slit end regions, each staggered slit defining and being flanked by complementary integral strap web portions offset in opposite n'ormail directions to present lengthwise opposed shoulders bordering the intermediate jog region of the slit, each joint having each of its nestable strap sections presenting a locking shoulder nestable within the jog region of the other strap section and enterable endwise into the opposing slit end region of said other section to establish one way interlocking engagement therebetween.

2. In a sealless strap connection between overlapped lengths of metal strap, a tandem array of longitudinally spaced shear lock joints, each joint being defined between nestable strap sections provided by matched integral portions of each length of metal strap, said nestable strap sections that define each joint being partly offset longitudinally to engage in one way mutually interlocking relation, each said nestable strap section having a single longitudinally oriented staggered slit comprised of lengthwise slit end regions and a lateral jog region joining the slit end regions, the staggered slits being aligned on each length of strap and each slit having an offset region of less than one-fifth of the strap width, each staggered slit defining and being flanked by complementary integral strap web portions offset in opposite normal directions to present lengthwise opposed shoulders bordering the intermediate jog region of the slit, each joint having each of its nestable strap sections presenting a locking shoulder nestable within the jog region of the other strap section and enterable endwise into the opposing slit end region of said other section to establish one way interlocking engagement therebetween and at least two of said joints having locking shoulders of substantially right angled configuration.

3. In a sealless strap connection between overlapped lengths of metal strap, a tandem array of longitudinally spaced shear lock joints, each joint being defined between nestable strap sections provided by matched integral po-rtions of each length of metal strap, said nestable strap sections that define each joint being partly offset longitudinally to engage in one way mutually interlocking relation, each said nestable strap section having a single longitudinally oriented staggered slit comprised of lengthwise slit end regions and a lateral jog region joining the slit end regions, the staggered slits being aligned and centered on each length of strap and each slit having an offset region of less than one-fifth of the strap width, each staggered slit defining and being flanked by complementary integral strap web portions offset in opposite normal directions to present lengthwise opposed shoulders bordering the intermediate jog region of the slit, each joint having each of its nestable strap sections presenting a locking shoulder nestable within the jog region of the other strap section and enterable endwise into the opposing slit end region of said other section to establish one way interlock ing engagement therebetween and at least two of said joints having locking shoulders of substantially right angled configuration.

References Cited by the Examiner UNITED STATES PATENTS 2,268,339 12/1941 Leslie 24-20 3,188,706 6/1965 Partridge 24-20 FOREIGN PATENTS 21,202 2/ 1935 Australia.

WILLIAM FELDMAN, Primary Examiner. J. L. JONES, Examiner. 

1. IN A SEALLESS STRAP CONNECTION BETWEEN OVERLAPPED LENGTHS OF METAL STRAP, A TANDEM ARRAY OF LONGITUDINALLY SPACED SHEAR LOCK JOINTS, EACH JOINT BEING DEFINED BETWEEN NESTABLE STRAP SECTIONS PROVIDED BY MATCHED INTEGRAL PORTIONS OF EACH LENGTH OF METAL STRAP, SAID NESTABLE STRAP SECTIONS THAT DEFINE EACH JOINT BEING PARTLY OFFSET LONGITUDINALLY TO ENGAGE IN ONE WAY MUTUALLY INTERLOCKING RELATION, EACH SAID NESTABLE STRAP SECTION HAVING A SINGLE LONGITUDINALLY ORIENTED STAGGERED SLIT COMPRISED OF LENGTHWISE SLIT END REGIONS AND A LATERAL JOG REGION JOINING THE SLIT END REGIONS, EACH STAGGERED SLIT DEFINING AND BEING FLANKED BY COMPLEMENTARY INTEGRAL STRAP WEB PORTIONS OFFSET IN OPPOSITE NORMAL DIRECTIONS TO PRESENT LENGTHWISE OPPOSED SHOULDERS BORDERING THE INTERMEDIATE JOG REGION OF THE SLIT, EACH JOINT HAVING EACH OF ITS NESTABLE STRAP SECTIONS PRESENTING A LOCKING SHOULDER NESTABLE WITHIN THE JOG REGION OF THE OTHER STRAP SECTION AND ENTERABLE ENDWISE INTO THE OPPOSING SLIT END REGION OF SAID OTHER SECTION TO ESTABLISH ONE WAY INTERLOCKING ENGAGEMENT THEREBETWEEN. 